> I don't give a crap if you've already used React, Redux, Express, whatever new flavor of the months are coming. If you're 23 and actively using them, odds are you're still going to be worth much less to my team than someone 40 who has to pick them up their first couple months but can immediately contribute valuable, hard-earned broadly-applicable timeless lessons about how to build and operate software.

Odds are fine, but they aren't a shortcut for using your brain. If a team's culture makes its members instantly side with either the 40 year old or the 23 year old when he/she makes a claim like "we don't need to write tests", "there are no problems in my code", or "we should convert our entire existing repo to <different style/library/language>", then that culture is stifling discussion and actively harming the quality of the code the team writes. Same applies to hiring decisions.

It's frustrating to see ageism swinging back and forth like a pendulum. There's value in having both the crystallised intelligence of older workers and the fluid intelligence of younger workers on one team, provided they firstly get hired and secondly manage to work together.